Optical waveguides in image sensors

ABSTRACT

An embodiment relates to an image sensor comprising (a) a optical pipe comprising a core and a cladding, and (b) a pair of photosensitive elements comprising a central photosensitive element and a peripheral photosensitive element, wherein the central photosensitive element is operably coupled to the core and the peripheral photosensitive element is operably coupled to the cladding, and methods of fabricating and using the same. The image sensor could further comprise a lens structure or an optical coupler or an optical coupler over the optical pipe, wherein the lens structure or the optical coupler or the optical coupler is operably coupled to the optical pipe.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/556,041 filed Jul. 23, 2012, which is a continuation of U.S. patentapplication Ser. No. 12/648,942, filed Dec. 29, 2009 (now U.S. Pat. No.8,229,255, issued Jul. 24, 2012), which is a continuation-in-part of andclaims the benefit of the earlier filing date of co-pending U.S. patentapplication Ser. No. 12/204,686, filed Sep. 4, 2008 (now U.S. Pat. No.7,646,943, issued Jan. 12, 2010), the entire contents of which areincorporated herein by reference.

This application is related to the disclosures of U.S. patentapplication Ser. No. 12/270,233, filed Nov. 13, 2008 (now U.S. Pat. No.8,274,039, issued Sep. 25, 2012), Ser. No. 13/925,429, filed Jun. 24,2013, Ser. No. 13/570,027, filed Aug. 8, 2012 (now U.S. Pat. No.8,471,190, issued Jun. 25, 2013), Ser. No. 12/472,264, filed May 26,2009 (now U.S. Pat. No. 8,269,985, issued Sep. 18, 2012), Ser. No.13/621,607, filed Sep. 17, 2012 (now U.S. Pat. No. 8,514,411, issuedAug. 20, 2013), Ser. No. 13/971,523, filed Aug. 20, 2013 (now U.S. Pat.No. 8,810,808, issued Aug. 19, 2014), Ser. No. 14/459,398, filed Aug.14, 2014, Ser. No. 12/472,271, filed May 26, 2009 (now abandoned), Ser.No. 12/478,598, filed Jun. 4, 2009 (now U.S. Pat. No. 8,546,742, issuedOct. 1, 2013), Ser. No. 14/021,672, filed Sep. 9, 2013 (now U.S. Pat.No. 9,177,985, issued Nov. 3, 2015), Ser. No. 12/573,582, filed Oct. 5,2009 (now U.S. Pat. No. 8,791,470, issued Jul. 29, 2014), Ser. No.14/274,448, filed May 9, 2014, Ser. No. 12/575,221, filed Oct. 7, 2009(now U.S. Pat. No. 8,384,007, issued Feb. 26, 2013), Ser. No.12/633,323, filed Dec. 8, 2009 (now U.S. Pat. No. 8,735,797, issued May27, 2014), Ser. No. 14/068,864, filed Oct. 31, 2013 (now U.S. Pat. No.9,263,613, issued Feb. 16, 2016), Ser. No. 14/281,108, filed May 19,2014 (now U.S. Pat. No. 9,123,841, issued Sep. 1, 2015), Ser. No.13/494,661, filed Jun. 12, 2012 (now U.S. Pat. No. 8,754,359, issuedJun. 17, 2014), Ser. No. 12/633,318, filed Dec. 8, 2009 (now U.S. Pat.No. 8,519,379, issued Aug. 27, 2013), Ser. No. 13/975,553, filed Aug.26, 2013 (now U.S. Pat. No. 8,710,488, issued Apr. 29, 2014), Ser. No.12/633,313, filed Dec. 8, 2009, Ser. No. 12/633,305, filed Dec. 8, 2009(now U.S. Pat. No. 8,299,472, issued Oct. 30, 2012), Ser. No.13/543,556, filed Jul. 6, 2012 (now U.S. Pat. No. 8,766,272, issued Jul.1, 2014), Ser. No. 14/293,164, filed Jun. 2, 2014, Ser. No. 12/621,497,filed Nov. 19, 2009 (now abandoned), Ser. No. 12/633,297, filed Dec. 8,2009 (now U.S. Pat. No. 8,889,455, issued Nov. 18, 2014), Ser. No.14/501,983 filed Sep. 30, 2014, Ser. No. 12/982,269, filed Dec. 30,2010, Ser. No. 12/966,573, filed Dec. 13, 2010 (now U.S. Pat. No.8,866,065, issued Oct. 21, 2014), Ser. No. 14/503,598, filed Oct. 1,2014, Ser. No. 12/967,880, filed Dec. 14, 2010 (now U.S. Pat. No.8,748,799, issued Jun. 10, 2014), Ser. No. 14/291,888, filed May 30,2014, Ser. No. 12/966,514, filed Dec. 13, 2010, Ser. No. 12/974,499,filed Dec. 21, 2010 (now U.S. Pat. No. 8,507,840, issued Aug. 13, 2013),Ser. No. 12/966,535, filed Dec. 13, 2010 (now U.S. Pat. No. 8,890,271,issued Nov. 18, 2014), Ser. No. 12/910,664, filed Oct. 22, 2010 (nowU.S. Pat. No. 9,000,353 issued Apr. 7, 2015), Ser. No. 14/632,739, filedFeb. 26, 2015, Ser. No. 12/945,492, filed Nov. 12, 2010, Ser. No.13/047,392, filed Mar. 14, 2011 (now U.S. Pat. No. 8,835,831, issuedSep. 16, 2014), Ser. No. 14/450,812, filed Aug. 4, 2014, Ser. No.13/048,635, filed Mar. 15, 2011 (now U.S. Pat. No. 8,835,905, issuedSep. 16, 2014), Ser. No. 13/106,851, filed May 12, 2011, Ser. No.13/288,131, filed Nov. 3, 2011, Ser. No. 14/334,848, filed Jul. 18,2014, Ser. No. 14/032,166, filed Sep. 19, 2013, Ser. No. 13/543,307,filed Jul. 6, 2012, Ser. No. 13/963,847, filed Aug. 9, 2013, Ser. No.13/693,207, filed Dec. 4, 2012, 61/869,727, filed Aug. 25, 2013, Ser.No. 14/322,503, filed Jul. 2, 2014, and Ser. No. 14/311,954, filed Jun.23, 2014, Ser. No. 14/563,781, filed Dec. 8, 2014, 61/968,816, filedMar. 21, 2014, Ser. No. 14/516,402, filed Oct. 16, 2014, Ser. No.14/516,162, filed Oct. 16, 2014, and 62/161,485, filed May 14, 2015 areeach hereby incorporated by reference in their entirety.

FIELD OF INVENTION

The embodiments relate to an integrated circuit manufacture, moreparticularly, to manufacturing more efficient CMOS image sensors.

BACKGROUND

An image sensor has a large number of identical sensor elements(pixels), generally greater than 1 million, in a Cartesian (square)grid. The distance between adjacent pixels is called the pitch (p). Thearea of a pixel is p². The area of the photosensitive element, i.e., thearea of the pixel that is sensitive to light for conversion to anelectrical signal, is normally only about 20% to 30% of the surface areaof the pixel.

The challenge of a designer is to channel as much of the light impingingon the pixel to the photosensitive element of the pixel. There are anumber of factors that diminish the amount of light from reaching thephotosensitive element. One factor is the manner in which the imagesensor is constructed. A complementary metal oxide semiconductor (CMOS)image sensor is manufactured by a process of etching and depositing anumber of layers of oxides of silicon, metal and nitride on top ofcrystalline silicon. The layers of a typical sensor are listed in TableI and shown in FIG. 1.

TABLE I Typical Layer Description Thickness (μm) 15 OVERCOAT 2.00 14MICRO LENS 0.773 13 SPACER 1.40 12 COLOR FILTER 1.20 11 PLANARIZATION1.40 10 PASS3 0.600 9 PASS2 0.150 8 PASS1 1.00 7 IMD5B 0.350 6 METAL331.18 5 IMD2B 0.200 4 METAL2 21.18 3 IMD1B 0.200 2 METAL1 1.18 1 ILD0.750

In Table I, typically the first layer on a silicon substrate is the ILDlayer and the topmost layer is the overcoat. In Table I, ILD refers to ainter-level dielectric layer, METAL1, METAL2 and METAL3 refer todifferent metal layers, IMD1B, IMD2B and IMD5B refer to differentinter-metal dielectric layers which are spacer layers, PASS1, PASS2 andPASS3 refer to different passivation layers (typically dielectriclayers).

The total thickness of the layers above the silicon substrate of theimage sensor is the stack height (s) of the image sensor and is the sumof the thickness of the individual layers. In the example of Table I,the sum of the thickness of the individual layers is about 11.6micrometers (μm).

The space above the photosensitive element of a pixel must betransparent to light to allow incident light from a full color scene toimpinge on the photosensitive element located in the silicon substrate.Consequently, no metal layers are routed across the photosensitiveelement of a pixel, leaving the layers directly above the photosensitiveelement clear.

The pixel pitch to stack height ratio (p/s) determines the cone of light(F number) that can be accepted by the pixel and conveyed to thephotosensitive element on the silicon. As pixels become smaller and thestack height increases, this number decreases, thereby lowering theefficiency of the pixel.

More importantly, the increased stack height with greater number ofmetal layers obscure the light from being transmitted through the stackto reach the photosensitive element, in particular of the rays thatimpinge the sensor element at an angle. One solution is to decrease thestack height by a significant amount (i.e., >2 μm). However, thissolution is difficult to achieve in a standard CMOS process.

Another issue, which possibly is the one that most limits theperformance of the conventional image sensors, is that less than aboutone-third of the light impinging on the image sensor is transmitted tothe photosensitive element such as a photodiode. In the conventionalimage sensors, in order to distinguish the three components of light sothat the colors from a full color scene can be reproduced, two of thecomponents of light are filtered out for each pixel using a filter. Forexample, the red pixel has a filter that absorbs green and blue light,only allowing red light to pass to the sensor.

DESCRIPTION OF THE FIGURES

FIG. 1 shows a cross sectional view of a conventional image sensor.

FIG. 2 shows a cross sectional view of an embodiment of an image sensor.

FIG. 3 shows a cross sectional view of another embodiment of an imagesensor having a microlens.

FIG. 4 shows a schematic cross section of a compound pixel having twoimage sensors having for two apertures (d₁ and d₂) with light pipes fordirecting light of different wavelengths (λ_(B) and λ_(R)).

FIG. 5 shows different schematic cross sectional view showing theconstruction of an embodiment of an image sensor.

FIG. 6 shows a schematic cross sectional view of an embodiment of a dualphotodiode comprising a first photodiode having substantially the same across sectional area as of the optical pipe is located beneath theoptical pipe and a second photodiode having substantially the same orgreater cross sectional areas than that of the aperture in the stack islocated under the first photodiode, and wherein the first photodiode andthe second photodiode are separated by a physical barrier to preventcross talk.

FIG. 7 shows a schematic cross sectional view of an embodiment of alight coupler optically coupled to an image sensor.

FIG. 8 shows different schematic cross sectional views showing theconstruction of an embodiment of a light coupler optically coupled to animage sensor. The top and bottom figures are cross sections of twocomplementary pixels (2 pipe lights of different diameters) that createcolor.

FIG. 9 shows a schematic of a top view of a device containing imagesensors of the embodiments disclosed herein, each image sensor havingtwo outputs representing the complementary colors.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here.

This disclosure is drawn, inter alia, to methods, apparatus, systems,and devices related to an image sensor and compound pixels. Anembodiment relates to a method for increasing the efficiency of an imagesensor. Another embodiment provides a means for eliminating the colorfilter so that more than only one-third of the impinging light is use toproduce an electrical signal. Another embodiment relates to a method forincreasing the efficiency of an image sensor by increasing the amount ofelectromagnetic radiation such as light impinging on the image sensor.An embodiment of the image sensor comprises an optical pipe such as alight pipe to transfer electromagnetic radiation incident on the imagesensor to the photosensitive element on or within the substrate of theimage sensor. The optical pipe include of a high refraction index corewith a lower refraction index cladding. The end of the optical pipeadjacent to the photosensitive element is about the same size as thephotosensitive element so that most or all of the electromagneticradiation in the pipe impinges on the photosensitive element. A couplerthat may take the shape of a micro lens efficiently could be located onthe optical pipe to collect and guide the electromagnetic radiation intothe optical pipe.

Another embodiment relates to use the optical pipe to eliminatepigmented color filters that absorb about ⅔ of the light that impingeson the image sensor. The core and the cladding of the optical pipe couldfunction as waveguides. Waveguides do not absorb light like colorfilters, but can be designed to selectively transmit selectedwavelengths.

A waveguide has a cutoff wavelength that is the lowest frequency thatthe waveguide can propagate. As a result, a waveguide in the core whosecutoff wavelength is at green will not propagate red light, and awaveguide in the core whose cutoff wavelength is at blue will notpropagate red and green light. In one implementation, a blue waveguideand a blue/green waveguide could be embedded within a white waveguide,which could be in the cladding. For example, any blue light could remainin the blue waveguide in a core, any blue or green light could remain inthe green/blue waveguide of another core, and the remainder of the lightcould remain in the white waveguide in one or more the claddings.

An embodiment relates to an image sensor comprising (a) a optical pipecomprising a core and a cladding, and (b) a pair of photosensitiveelements comprising a central photosensitive element and a peripheralphotosensitive element, wherein the central photosensitive element isoperably coupled to the core and the peripheral photosensitive elementis operably coupled to the cladding. Preferably, the image sensorcomprises no color filter, or optionally it could comprise a colorfilter. Preferably, the optical pipe is circular, non-circular orconical. Preferably, the core has a core index of refraction (n₁) andthe cladding has a cladding index of refraction (n₂), and furtherwherein n₁ is greater than n₂. Preferably, the optical pipe isconfigured to separate wavelengths of an electromagnetic radiation beamincident on the image sensor at a cutoff wavelength through the core andthe cladding. Preferably, the optical pipe is configured to separatewavelengths of an electromagnetic radiation beam incident on the imagesensor at a cutoff wavelength through the core and the cladding withouta color filter. Preferably, an electromagnetic radiation beam receivingend of the optical pipe comprises a curved surface. Preferably, the corehas a greater cross-sectional area at an electromagnetic radiation beamreceiving end of the core than that at an electromagnetic radiation beamemitting end of the core. Preferably, the pair of photosensitiveelements are located on or within a substrate.

The image sensor could further comprise a lens structure or an opticalcoupler over the optical pipe, wherein the lens structure or the opticalcoupler is operably coupled to the optical pipe. Preferably, the corecomprises a first waveguide having a cutoff wavelength such thatelectromagnetic radiation of wavelength greater than the cutoffwavelength leaks out from the core into the cladding. Preferably, thecladding comprises a second waveguide that permits electromagneticradiation of wavelength of greater than the cutoff wavelength to remainswithin the cladding and be transmitted to the peripheral photosensitiveelement. Preferably, a cross-sectional area of the core at anelectromagnetic radiation beam emitting end of the core is substantiallyequal to an area of the central photosensitive element. Preferably, across-sectional area of the cladding at an electromagnetic radiationbeam emitting end of the cladding is substantially equal to an area ofthe peripheral photosensitive element.

The image sensor could further comprise a stack surrounding the opticalpipe, the stack comprising metallic layers embedded in dielectriclayers, wherein the dielectric layers have a lower refractive index thanthat of the cladding. Preferably, a surface of the stack comprises areflective surface. Preferably, the image sensor is a complementarymetal oxide semiconductor (CMOS) image sensor. Preferably, the opticalis could also be used for charge-coupled devices (CCD). Preferably, anamount of an electromagnetic radiation beam impinging on the imagesensor is transmitted to the photosensitive element is greater thanabout a third of the electromagnetic radiation beam impinging on theimage sensor. Preferably, the core has a core index of refraction (n₁),the cladding has a cladding index of refraction (n₂), and the stack hasa stack refractive index (n₃), and further wherein n₁>n₂>n₃. Preferably,the photosensitive element comprises a photodiode. Preferably, the coreis the first waveguide and the cladding is the second waveguide.Preferably, the lens structure or the optical coupler comprises a curvedsurface and a flat surface such that the lens structure or the opticalcoupler is shaped as a stationary liquid droplet. Preferably, the lensstructure or the optical coupler comprises a first opening and a secondopening with the first opening being larger than the second opening, anda connecting surface extending between the first and second openings.Preferably, a diameter of the first opening is substantially the same asa diameter of the cladding and a diameter of the second opening issubstantially the same as a diameter of the core. Preferably, theconnecting surface is flat or curved. Preferably, the connecting surfacecomprises a reflective surface.

Another embodiment relates to a compound pixel comprising at least twodifferent image sensors, each image sensor comprising (a) a optical pipecomprising a core and a cladding, and (b) a pair of photosensitiveelements comprising a central photosensitive element and a peripheralphotosensitive element, wherein the central photosensitive element isoperably coupled to the core and the peripheral photosensitive elementis operably coupled to the cladding, wherein each of the at least twodifferent image sensors is configured to separate wavelengths of anelectromagnetic radiation beam incident on the compound pixel at acutoff wavelength, and the compound pixel is configured to reconstruct aspectrum of wavelengths of the electromagnetic radiation beam.Preferably, the core comprises a first waveguide having the cutoffwavelength such that electromagnetic radiation of wavelength greaterthan the cutoff wavelength leaks out from the core into the cladding,further wherein the cutoff wavelength of the core of each of the atleast two different image sensors is different such that the at leasttwo different image sensors separate the electromagnetic radiation beamincident on the compound pixel at different cutoff wavelengths.Preferably, the cladding comprises a second waveguide that permitselectromagnetic radiation of wavelength of greater than the cutoffwavelength to remains within the cladding and be transmitted to theperipheral photosensitive element. Preferably, a cross-sectional area ofthe cladding at an electromagnetic radiation beam emitting end of thecladding is substantially equal to an area of the peripheralphotosensitive element. The compound pixel could further comprise astack of metallic and non-metallic layers surrounding the optical pipeof each of the at least two different optical sensors.

Another embodiment relates to a compound pixel comprising at least afirst image sensor and a second image sensor, wherein the first imagesensor is configured to provide a first separation of an electromagneticradiation beam incident on the image sensor at a first cutoff wavelengthwithout any color filter, the second image sensor is configured toprovide a second separation of the electromagnetic radiation beamincident on the image sensor at a second cutoff wavelength without anycolor filter, the first cutoff wavelength is different from the secondcutoff wavelength, and the compound pixel is configured to reconstruct aspectrum of wavelengths of the electromagnetic radiation beam.Preferably, the first image sensor comprises a first waveguide havingthe first cutoff wavelength such that electromagnetic radiation ofwavelength greater than the first cutoff wavelength leaks out from thefirst waveguide, wherein the second image sensor comprises a secondwaveguide having the second cutoff wavelength such that electromagneticradiation of wavelength greater than the second cutoff wavelength leaksout from the second, further wherein the first cutoff wavelength isdifferent from the second cutoff wavelength. Preferably, the first imagesensor further comprises a first white waveguide that permitselectromagnetic radiation of wavelength of greater than the first cutoffwavelength to remains within the first white waveguide and the secondimage sensor further comprises a second white waveguide that permitselectromagnetic radiation of wavelength of greater than the secondcutoff wavelength to remains within the second white waveguide.Preferably, the first image sensor comprises a first pair ofphotosensitive elements and the second image sensor comprises a secondpair of photosensitive elements. The compound pixel could furthercomprise a stack of metallic and non-metallic layers in the vicinity ofthe first and second waveguides. Preferably, the two different imagesensors comprise cores of different diameters. Preferably, the firstimage sensor comprises a core of a different diameter than that of thesecond image sensor.

Another embodiment relates to a method of manufacturing an image sensor,comprising (a) forming a pair of photosensitive elements comprising acentral photosensitive element and a peripheral photosensitive element,and (b) forming a optical pipe comprising a core and a cladding, whereinthe central photosensitive element is operably coupled to the core andthe peripheral photosensitive element is operably coupled to thecladding.

The embodiments relate to a high efficiency image sensor and a methodfor increasing the efficiency of an image sensor. The efficiency couldbe increased when more of the light impinging on an image sensor isreceived by the photosensitive element and converted to an electricalsignal.

The method of manufacturing an embodiment of the image sensor (FIG. 2)comprises the formation of an optical pipe using the principles of anoptical fiber waveguide. As shown in FIG. 2, an optical pipe comprises ahigh refraction index core channel (22) that extends from the end of theimage sensor receiving incident electromagnetic radiation beam, e.g.,overcoat (15), down to the photosensitive element (24) on or within thesubstrate (20) with a cladding layer (26) of lower refraction indexmaterial surrounding the core. In the image sensor of the embodimentsdisclosed herein, the color filter (12) in FIG. 2 would be optional, andpreferably not be included.

Each of the photosensitive elements (photosensors) typically comprises aphotodiode, although not limited to only a photodiode. Typically, thephotodiode is doped to a concentration from about 1e(E)16 to about1e(E)18 dopant atoms per cubic centimeter, while using an appropriatedopant.

The layers 1-11 in FIG. 2 illustrate different stacking layers similarto layers 1-11 of FIG. 1. The stacking layers comprise dielectricmaterial-containing and metal-containing layers. The dielectricmaterials include as but not limited to oxides, nitrides and oxynitridesof silicon having a dielectric constant from about 4 to about 20,measured in vacuum. Also included, and also not limiting, are generallyhigher dielectric constant gate dielectric materials having a dielectricconstant from about 20 to at least about 100. These higher dielectricconstant dielectric materials may include, but are not limited tohafnium oxides, hafnium silicates, titanium oxides, barium-strontiumtitanates (BSTs) and lead-zirconate titanates (PZTs).

The dielectric material-containing layers may be formed using methodsappropriate to their materials of composition. Non-limiting examples ofmethods include thermal or plasma oxidation or nitridation methods,chemical vapor deposition methods (including atomic layer chemical vapordeposition methods) and physical vapor deposition methods.

The metal-containing layers could function as electrodes. Non-limitingexamples include certain metals, metal alloys, metal silicides and metalnitrides, as well as doped polysilicon materials (i.e., having a dopantconcentration from about 1e18 to about 1e22 dopant atoms per cubiccentimeter) and polycide (i.e., doped polysilicon/metal silicide stack)materials. The metal-containing layers may be deposited using any ofseveral methods. Non-limiting examples include chemical vapor depositionmethods (also including atomic layer chemical vapor deposition methods)and physical vapor deposition methods. The metal-containing layers couldcomprise a doped polysilicon material (having a thickness typically inthe range 1000 to 1500 Angstrom) from about 1000 to about 1500angstroms.

The dielectric and metallization stack layer comprises a series ofdielectric passivation layers. Also embedded within the stack layer areinterconnected metallization layers. Components for the pair ofinterconnected metallization layers include, but are not limited tocontact studs, interconnection layers, interconnection studs.

The individual metallization interconnection studs and metallizationinterconnection layers that could be used within the interconnectedmetallization layers may comprise any of several metallization materialsthat are conventional in the semiconductor fabrication art. Non-limitingexamples include certain metals, metal alloys, metal nitrides and metalsilicides. Most common are aluminum metallization materials and coppermetallization materials, either of which often includes a barriermetallization material, as discussed in greater detail below. Types ofmetallization materials may differ as a function of size and locationwithin a semiconductor structure. Smaller and lower-lying metallizationfeatures typically comprise copper containing conductor materials.Larger and upper-lying metallization features typically comprisealuminum containing conductor materials.

The series of dielectric passivation layers may also comprise any ofseveral dielectric materials that are conventional in the semiconductorfabrication art. Included are generally higher dielectric constantdielectric materials having a dielectric constant from 4 to about 20.Non-limiting examples that are included within this group are oxides,nitrides and oxynitrides of silicon. For example, the series ofdielectric layers may also comprise generally lower dielectric constantdielectric materials having a dielectric constant from about 2 to about4. Included but not limiting within this group are hydrogels, aerogels,silsesquioxane spin-on-glass dielectric materials, fluorinated glassmaterials and organic polymer materials.

Typically, the dielectric and metallization stack layer comprisesinterconnected metallization layers and discrete metallization layerscomprising at least one of copper metallization materials and aluminummetallization materials. The dielectric and metallization stack layeralso comprises dielectric passivation layers that also comprise at leastone of the generally lower dielectric constant dielectric materialsdisclosed above. The dielectric and metallization stack layer could havean overall thickness from about 1 to about 4 microns. It may comprisefrom about 2 to about 4 discrete horizontal dielectric and metallizationcomponent layers within a stack.

The layers of the stack layer could be patterned to form patterneddielectric and metallization stack layer using methods and materialsthat are conventional in the semiconductor fabrication art, andappropriate to the materials from which are formed the series ofdielectric passivation layers. The dielectric and metallization stacklayer may not be patterned at a location that includes a metallizationfeature located completely therein. The dielectric and metallizationstack layer may be patterned using wet chemical etch methods, dry plasmaetch methods or aggregate methods thereof. Dry plasma etch methods aswell as e-beam etching if the dimension needs to be very small, aregenerally preferred insofar as they provide enhanced sidewall profilecontrol when forming the series of patterned dielectric andmetallization stack layer.

The planarizing layer 11 may comprise any of several opticallytransparent planarizing materials. Non-limiting examples includespin-on-glass planarizing materials and organic polymer planarizingmaterials. The planarizing layer 11 could extend above the optical pipesuch that the planarizing layer 11 would have a thickness sufficient toat least planarize the opening of the optical pipe 22, thus providing aplanar surface for fabrication of additional structures within the CMOSimage sensor whose schematic cross-sectional diagram is illustrated inFIG. 2. The planarizing layer could be patterned to form the patternedplanarizing layer.

Optionally, as shown in FIG. 2, there could be a series of color filterlayers 12 located upon the patterned planarizing layer 11. The colorfilter layers are registered with respect to the photosensor regions 24.Color filter layer 12 while present is not registered with respect toany photosensor region. The series of color filter layers, if present,would typically include either the primary colors of red, green andblue, or the complementary colors of yellow, cyan and magenta. Theseries of color filter layers would typically comprise a series of dyedor pigmented patterned photoresist layers that are intrinsically imagedto form the series of color filter layers. Alternatively, the series ofcolor filter layers may comprise dyed or pigmented organic polymermaterials that are otherwise optically transparent, but extrinsicallyimaged while using an appropriate mask layer. Alternative color filtermaterials may also be used. The filter could also be filter for a blackand white or IR sensors, wherein the filter cuts off visible and pass IRpredominantly.

The spacer layer (13) could be one or more layers made of any materialthat physically, but not optically, separates the stacking layers fromthe micro lens (14). The spacer layer could be formed of a dielectricspacer material or a laminate of dielectric spacer materials, althoughspacer layers formed of conductor materials are also known. Oxides,nitrides and oxynitrides of silicon are commonly used as dielectricspacer materials. Oxides, nitrides and oxynitrides of other elements arenot excluded. The dielectric spacer materials may be deposited usingmethods analogous, equivalent or identical to the methods describedabove. The spacer layer could be formed using a blanket layer depositionand etchback method that provides the spacer layer with thecharacteristic inward pointed shape.

The micro lens (14) may comprise any of several optically transparentlens materials that are known in the art. The lens layers may compriseany of several optically transparent lens materials that are known inthe art. Non-limiting examples include optically transparent inorganicmaterials, optically transparent organic materials and opticallytransparent composite materials. Most common are optically transparentorganic materials. Typically the lens layers could be formed incident topatterning and reflow of an organic polymer material that has a glasstransition temperature lower than the series of color filter layers 12,if present, or the patterned planarizing layer 11.

In the optical pipe 22, the high index material could, for example, besilicon nitride having a refractive index of about 2.0. The lower indexcladding layer material could, for example, be a glass, for example amaterial selected from Table II, having a refractive index about 1.5.

TABLE II Typical Material Index of Refraction Micro Lens (Polymer) 1.583Spacer 1.512 Color Filter 1.541 Planarization 1.512 PESiN 2.00 PESiO1.46 SiO 1.46In Table II, PESiN refers to plasma enhanced SiN and PESiO refers toplasma enhanced SiO.

Preferably, the cross sectional area of the end of the optical pipeadjacent to the photosensitive element is about the same size as thearea of the photosensitive element. Otherwise, electromagnetic radiationguided through the optical pipe outside of the photosensitive elementcould impinge on non-sensitive regions of the substrate, therebyreducing the amount of light converted to an electrical signal andreducing the efficiency of the image sensor.

Optionally, a micro lens could be located on the optical pipe near theincident electromagnetic radiation beam receiving end of the imagesensor. The function of the micro lens or in more general terms is to bea coupler, i.e., to couple the incident electromagnetic radiation beaminto the optical pipe. If one were to choose a micro lens as thecoupler, its distance from the optical pipe would be much shorter thanto the photosensitive element, so the constraints on its curvature aremuch less stringent, thereby making it implementable with existingfabrication technology.

The shape of the optical pipe could be different for differentembodiments. In one configuration, the optical pipe could cylindrical,that is, the diameter of the pipe remains the substantially the samethroughout the length of the optical pipe. In another configuration, theoptical pipe could conical, where the upper diameter of the crosssectional area of the optical pipe could be greater than the lowerdiameter of the cross sectional area of the optical pipe. The terms“upper” and “lower” refer to the ends of the optical pipe located closerto the incident electromagnetic radiation beam receiving and exitingends of the image sensor. Other shapes include a stack of conicalsections.

Table II lists several different glasses and their refractive indices.These glasses could be used for the manufacture of the optical pipe suchthat refractive index of the core is higher than that of the cladding.The CMOS image sensors of the embodiments could be fabricated usingdifferent transparent glasses having different refractive indiceswithout the use of pigmented color filters. As waveguides of theembodiments do not absorb light like color filters, but may be designedto selectively transmit selected wavelengths, the light transmissionefficiency of the optical pipe could be at least 50%, more preferably atleast 75%, most preferably at least 99%, i.e., substantially 100%. Withthe proper arrangement of waveguides in the optical pipe of theembodiments, it is possible to more efficiently transmit theelectromagnetic radiation beam incident on the image sensor to thephotosensitive element, thereby increasing the sensitivity of thesensor.

In some embodiments, the optical pipe could be circular in or crosssection so as to function as a circular waveguide characterized by thefollowing parameters: (1) the core radius (Rc); (2) the core index ofrefraction (n₁); and (3) the cladding index of refraction (n₂). Theseparameters could generally determine the wavelength of light that canpropagate through the waveguide. A waveguide has a cutoff wavelength,λct. The portion of the incident electromagnetic radiation havingwavelengths longer than the cutoff wavelength would not be confined withthe core. As a result, an optical pipe that functions as a waveguidewhose cutoff wavelength is at green will not propagate red light thoughthe core, and an optical pipe that functions as a waveguide whose cutoffwavelength is at blue will not propagate red and green light through thecore.

By nesting optical pipes that function as waveguides and using a microlens coupler as shown in FIG. 3, an array of image sensors could beconfigured to obtain complementary colors having wavelengths ofelectromagnetic radiation separated at a cutoff wavelength in the coreand cladding of each optical pipe of every image sensor. Thecomplementary colors are generally two colors when mixed in the properproportion produce a neutral color (grey, white, or black). Thisconfiguration also enables the capture and guiding of most of theelectromagnetic radiation incident beam impinging on the micro lens tothe photosensitive elements (i.e., photodiodes) located at the lower endof the optical pipe. Two adjacent or substantially adjacent imagesensors with different color complementary separation can providecomplete information to reconstruct a full color scene according toembodiments described herein. This technology of embodiments disclosedherein can further supplant pigment based color reconstruction for imagesensing which suffers from the inefficiency of discarding (throughabsorption) the non selected color for each pixel.

Each physical pixel of a device containing an image sensor of theembodiments disclosed herein would have two outputs representing thecomplementary colors, e.g., (cyan, red) designated as output type 1 or(yellow, blue) designated as output type 2. These outputs would bearranged as follows:

1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 . . . 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 .. . 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Each physical pixel would have complete luminance information obtainedby combining its two complementary outputs. As a result, the same imagesensor can be used either as a full resolution black and white or fullcolor sensor.

In the embodiments of the image sensors disclosed herein, the fullspectrum of wavelengths of the incident electromagnetic radiation beam(e.g., the full color information of the incident light) could beobtained by the appropriate combination of two adjacent pixels eitherhorizontally or vertically as opposed to 4 pixels for the conventionalBayer pattern.

The image sensors of the embodiments disclosed herein would have athree-fold impact on the future of CMOS image sensor technology.

The first impact would be the increase in the F-number, or the lightacceptance cone of each pixel, thereby increasing the overall efficiencyof the sensor. Also, with the embodiments disclosed herein, the F-numberof the sensor would be relatively insensitive to stack height (distanceof the surface of the micro lens to the photodiode). Thus, stack eightsof 10 microns or greater could be easily accommodated.

The second impact would be the elimination of color filters (unlessdesired for some other purposes) whose light absorption characteristicsreduce the sensitivity of the conventional image sensor by about afactor of three.

The third impact would stem from the fact that advanced CMOS fabricationprocesses use metals and materials that may compromise the transparencyof the electromagnetic radiation beam such as light propagating throughall the metal layers stacked on top of the photoelectric element such asa photodiode. An optical pipe of the embodiments disclosed herein wouldprovide a solution to this problem. Also, the system of the embodimentsdisclosed herein would decouple the light path of the image sensor,i.e., the optical pipe, from impurities that may be introduced duringfabrication of patterned stacked layers of the image sensor. The opticalpipe itself, however, should be fabricated with low transmission lossmaterials such as glasses.

Depending on minimum transistor sizes, each pixel containing an imagesensor of the embodiments disclosed herein could be as small as 1 micronor less in pitch and yet have sufficient sensitivity. This could openthe way for contact imaging of very small structures such as biologicalsystems.

The embodiments, which include a plurality of embodiments of an imagesensor, preferably a CMOS image sensor, as well as methods forfabrication thereof, will be described in further detail within thecontext of the following description. The description is furtherunderstood within the context of the drawings described above. Thedrawings are for illustrative purposes and as such are not necessarilydrawn to scale.

FIG. 4 (same as FIG. 5(B)) shows a schematic cross section of anembodiment of a compound pixel having two image sensors having twoapertures (d₁ and d₂) with light pipes for directing light of differentwavelengths (λ_(B) and λ_(R)). Two photodiodes are constructed undereach aperture to capture light of wavelength λ_(B) (or λ_(R)) and of thelight of wave length λ_(w-B) (or λ_(w-R)). Note that (w) refers to thewavelength of white light. Signals from the 4 photodiodes (located in 2pixels) are used to construct color.

FIGS. 5(A) to 5(G) show a series of schematic cross-sectional diagramsillustrating the results of progressive stages in fabricating a CMOSimage sensor in accordance with an embodiment of the invention. FIG.5(A) in particular shows a schematic cross-sectional diagram of the CMOSimage sensor at an early stage in the fabrication when photodiodes areconstructed. The photodiodes are of an area consistent with the area ofthe light pipes to be fabricated overlying the photodiodes.

FIG. 5(A) shows a semiconductor substrate. The substrate could include acounter-doped well (having a conductivity type different from thesemiconductor substrate) is located within the semiconductor substrate(not shown in FIG. 5(A)). A series of isolation regions could also belocated within the semiconductor substrate. The semiconductor substratecould comprise a first region R1 that comprises a photoactive region(shown in FIG. 5(A)) and a laterally adjacent second region R2 thatcomprises a circuitry region (not shown in FIG. 5(A)).

Within the photoactive region R1, the series of isolation regionsseparates a series of photosensor regions (i.e., the dual photodiodesshown in FIG. 5(A)). Within the circuitry region R2, the series ofisolation regions could separate a pair of active regions. The pair ofactive regions could include a first field effect transistor T1 and asecond field effect transistor T2 located and fabricated therein. Thefield effect transistors T1 and T2 could comprise a pair of CMOStransistors, since transistor T1 could be located and fabricated withinthe semiconductor substrate and transistor T2 could located andfabricated within the doped well (having different conductivity typethan the semiconductor substrate). Finally, there could be a blanketetch stop layer located conformally covering the first region R1 and thesecond region R2 including the structures that comprise the field effecttransistors T1 and T2.

Within both the photoactive region R1 and the circuitry region R2, theseries of isolation regions 12 may comprise materials, have dimensionsand be formed using methods that are otherwise conventional in thesemiconductor fabrication art.

The series of isolation regions may comprise isolation regions includingbut not limited to local oxidation of silicon (LOCOS) isolation regions,shallow trench isolation regions (i.e., having a depth up to about 5000angstroms) and deep trench isolation regions (i.e., having a depth up toabout 60000 angstroms). Typically, the first embodiment uses shallowtrench isolation regions that are located within shallow isolationtrenches. The isolation regions (whether located within shallowisolation trenches or deep isolation trenches) may comprise any ofseveral dielectric materials. Typically included are oxides, nitridesand oxynitrides of silicon, as well as laminates thereof and compositesthereof. Oxides, nitrides and oxynitrides of other elements are notexcluded.

The series of isolation regions could be formed at least in part using ablanket layer deposition and planarizing method. Appropriate blanketlayers may be formed using thermal or plasma oxidation or nitridationmethods, chemical vapor deposition methods and physical vapor depositionmethods. Planarization methods may include, but are not limited tomechanical planarizing methods, and chemical mechanical polish (CMP)planarizing methods. Chemical mechanical polish planarizing methods aremost common.

Within the photoactive region R1, each of the series of photosensorregions may comprise photosensors that are otherwise generallyconventional in the semiconductor fabrication art. Each of thephotosensors typically comprises a photodiode, although the invention isnot limited to a photosensor region as only a photodiode. Thephotodiodes could be doped to a concentration from about 1e(E)16 toabout 1e(E)18 dopant atoms per cubic centimeter, while using anappropriate dopant.

Within the circuitry region R2, each of the pair of field effecttransistors T1 and T2 could comprise a gate dielectric layer locatedupon the semiconductor substrate. A gate electrode could be located uponthe gate dielectric layer. Spacer layers could be located adjoining thesidewalls of the gate dielectric layer and the gate electrode. Finally,each of the first transistor T1 and the second transistor T2 couldcomprise a pair of source/drain regions separated by a channel regionlocated beneath the gate electrode.

Each of the foregoing layers and structures that comprise that firsttransistor T1 and the second transistor T2 may comprise materials andhave dimensions that are conventional in the semiconductor fabricationart. Each of the foregoing layers and structures that comprise the firsttransistor T1 and the second transistor T2 may also be formed usingmethods that are conventional in the semiconductor fabrication art.

The gate dielectric layers may comprise any of several gate dielectricmaterials. Included but not limiting are generally lower dielectricconstant gate dielectric materials such as but not limited to oxides,nitrides and oxynitrides of silicon having a dielectric constant fromabout 4 to about 20, measured in vacuum. Also included, and also notlimiting, are generally higher dielectric constant gate dielectricmaterials having a dielectric constant from about 20 to at least about100. These higher dielectric constant dielectric materials may include,but are not limited to hafnium oxides, hafnium silicates, titaniumoxides, barium-strontium titanates (BSTs) and lead-zirconate titanates(PZTs).

The foregoing gate dielectric materials may be formed using methodsappropriate to their materials of composition. Non-limiting examples ofmethods include thermal or plasma oxidation or nitridation methods,chemical vapor deposition methods (including atomic layer chemical vapordeposition methods) and physical vapor deposition methods. Typically,the gate dielectric layers could comprise a thermal silicon oxide gatedielectric material having a thickness from about 20 to about 70angstroms.

The gate electrodes may similarly also comprise any of several gateelectrode conductor materials. Non-limiting examples include certainmetals, metal alloys, metal silicides and metal nitrides, as well asdoped polysilicon materials (i.e., having a dopant concentration fromabout 1e18 to about 1e22 dopant atoms per cubic centimeter) and polycide(i.e., doped polysilicon/metal silicide stack) materials. The gateelectrode materials may be deposited using any of several methods.Non-limiting examples include chemical vapor deposition methods (alsoincluding atomic layer chemical vapor deposition methods) and physicalvapor deposition methods. Typically, each of the gate electrodes 18comprises a doped polysilicon material having a thickness from about1000 to about 1500 angstroms.

The spacer layers could be typically formed of a dielectric spacermaterial or a laminate of dielectric spacer materials, although spacerlayers formed of conductor materials are also known. Oxides, nitridesand oxynitrides of silicon are commonly used as dielectric spacermaterials. Oxides, nitrides and oxynitrides of other elements are notexcluded. The dielectric spacer materials may be deposited using methodsanalogous, equivalent or identical to the methods used for forming thegate dielectric layers. Typically, the spacer layers could be formedusing a blanket layer deposition and etchback method that provides thespacer layers with the characteristic inward pointed shape.

The source/drain regions could be formed using a two-step ionimplantation method. The source/drain regions could be implanted at apolarity appropriate to a field effect transistor within which they areformed. The two step ion implantation method uses the gate electrode,with and without the spacer layers, as a mask. Typical concentrations ofdopants within the source/drain regions could be from about 1c(E)15 toabout 1c(E)22 dopant atoms per cubic centimeter.

The blanket etch stop layer may comprise etch stop materials that areconventional in the semiconductor fabrication art. Non-limiting examplesalso include oxides, nitrides and oxynitrides of silicon. Oxides,nitrides and oxynitrides of other elements are also not excluded. Aparticular composition of the etch stop layer could be selected inaccordance with a composition of materials located and formed thereover.Thus in light of further disclosure below, the blanket etch stop layercould comprise a nitride etch stop material, although the invention isnot so limited. The blanket etch stop layer may be formed using any ofseveral methods. Non-limiting examples include chemical vapor depositionor physical vapor deposition methods. Typically, the blanket etch stoplayer comprises a silicon nitride material that has a thickness fromabout 100 to about 300 angstroms.

FIG. 5(B) shows the results of further processing of the CMOS imagesensor whose schematic cross-sectional diagram is illustrated in FIG.5(A). FIG. 5(B) shows dielectric and metal connections stack, patternedand made of materials commonly used in fabricating CMOS sensors.

FIG. 5(B) shows a dielectric and metallization stack layer located uponthe CMOS image sensor whose schematic cross-sectional diagram isillustrated in FIG. 5(A). The dielectric and metallization stack layercomprises a series of dielectric passivation layers. Embedded within theseries of dielectric passivation layers includes interconnectedmetallization layers. Components for the interconnected metallizationlayers include, but are not limited to contact studs CA, firstinterconnection layers M1, first interconnection studs V1, secondinterconnection layers M2, second interconnection studs V2, thirdinterconnection layers M3, terminal interconnection studs V3 andterminal metallization layers M4. One interconnected metallization layercould be connected to a source/drain region of transistor T1 and anotherinterconnected metallization layer could be connected to a source/drainregion of transistor T2. A pair of first interconnection layers M1, apair of second interconnection layers M2 and a pair of thirdinterconnection layers M3 is also located remotely within thephotosensor region R1, but still embedded within the dielectric andmetallization stack layer shown in FIG. 5(B).

The individual metallization interconnection studs and metallizationinterconnection layers CA, M1, V1, M2, V2, M3, V3 and M4 that could beused within the interconnected metallization layers may comprise any ofseveral metallization materials that are conventional in thesemiconductor fabrication art. Non-limiting examples include certainmetals, metal alloys, metal nitrides and metal silicides. Most commonare aluminum metallization materials and copper metallization materials,either of which often includes a barrier metallization material, asdiscussed in greater detail below. Types of metallization materials maydiffer as a function of size and location within a semiconductorstructure. Smaller and lower-lying metallization features typicallycomprise copper containing conductor materials. Larger and upper-lyingmetallization features typically comprise aluminum containing conductormaterials.

The series of dielectric passivation layers the stack may also compriseany of several dielectric materials that are conventional in thesemiconductor fabrication art. Included are generally higher dielectricconstant dielectric materials having a dielectric constant from 4 toabout 20. Non-limiting examples that are included within this group areoxides, nitrides and oxynitrides of silicon. The series of dielectriclayers may also comprise generally lower dielectric constant dielectricmaterials having a dielectric constant from about 2 to about 4. Includedbut not limiting within this group are hydrogels, aerogels,silsesquioxane spin-on-glass dielectric materials, fluorinated glassmaterials and organic polymer materials.

The dielectric and metallization stack layer could compriseinterconnected metallization layers and discrete metallization layersM1, M2 and M3 comprising at least one of copper metallization materialsand aluminum metallization materials. The dielectric and metallizationstack layer may also comprise dielectric passivation layers that alsocomprise at least one of the generally lower dielectric constantdielectric materials disclosed above. The dielectric and metallizationstack layer could have an overall thickness from about 1 to about 4microns (μm). It may typically comprise from about 2 to about 4 discretehorizontal dielectric and metallization component layers within a stack.

FIG. 5(C) shows a schematic cross-sectional diagram illustrating theresults of further processing of the CMOS image sensor whose schematiccross-sectional diagram is illustrated in FIG. 5(B).

FIG. 5(C) shows the results of patterning the dielectric andmetallization stack layer to form a patterned dielectric andmetallization stack layer that comprises a series of patterneddielectric passivation layers. The patterned dielectric andmetallization stack layer has a series of apertures A1 and A2 locatedtherein and registered with the series of photosensor regions.

The patterned dielectric and metallization stack layer may be patternedfrom the dielectric and metallization stack layer while using methodsand materials that are conventional in the semiconductor fabricationart, and appropriate to the materials from which are formed the seriesof dielectric passivation layers. The dielectric and metallization stacklayer may be patterned using wet chemical etch methods, dry plasma etchmethods or aggregate methods thereof. Dry plasma etch methods aregenerally preferred insofar as they provide enhanced sidewall profilecontrol when forming the series of patterned dielectric andmetallization stack layer. As is illustrated in FIG. 5(C), thedielectric and metallization stack layer could be patterned to form thepatterned dielectric and metallization stack layer while using an etchstop layer as a stop layer.

FIG. 5(D) shows the results of further processing of the CMOS imagesensor whose schematic cross-sectional diagram is illustrated in FIG.5(C).

FIG. 5(D) shows the apertures are filled with materials of high lightindex of refraction (n1). Optionally, in one embodiment, a reflectivelayer having a reflective surface conformally and contiguously liningeach of the apertures A1 and A2, including the bottoms and sidewallsthereof, and also conformally and contiguously covering top surfaces ofthe patterned dielectric and metallization stack layer could be formed.The reflective layer could also passivate a terminal metal layer M4.

Dielectric materials within the series of patterned dielectric andmetallization stack layer typically have dielectric constants from about1.4 to about 1.6 (e.g., when comprised of silicon oxide). Aperture fillmaterials of high light refraction (n1) could have a dielectric constantfrom about 1.6 to about 2.1. A silicon nitride dielectric materialtypically has a dielectric constant from about 2.0 to about 2.1, andcould be used for forming the high light refraction material fillingapertures, but the embodiment is not so limited.

FIG. 5(E) shows the results of further processing of the CMOS imagesensor whose schematic cross-sectional diagram is illustrated in FIG.5(D). Specifically, FIG. 5(E) shows the results of patterning the highlight refraction material in apertures A1 and A2 such that material isremoved to leave a light pipe structure of high light index ofrefraction (n1). The foregoing patterning may be implemented usingmethods and materials that are conventional in the art. Non-limitingexamples include wet chemical etch methods and materials, dry plasmaetch methods and materials, and aggregate methods and materials thereof.Alternate methods are not excluded.

FIG. 5(F) shows the results of further processing of the CMOS imagesensor whose schematic cross-sectional diagram is illustrated in FIG.5(E). Specifically, FIG. 5(F) shows that the volume around the lightpipe is filled with material of index of refraction (n2<n1). Optionally,in one embodiment, it is also possible to leave this volume unfilled.

Optionally, in one embodiment, a planarizing layer could be located uponthe reflective layer and/or above filled apertures. The planarizinglayer may comprise any of several optically transparent planarizingmaterials. Non-limiting examples include spin-on-glass planarizingmaterials and organic polymer planarizing materials. The planarizinglayer could have a thickness sufficient to at least planarize the seriesof apertures A1 and A2, thus providing a planar surface for fabricationof additional structures within the CMOS image sensor.

FIG. 5(G) shows the embodiment in which a reflective layer could bedeposited on the stack as discussed above such that the sidewalls of theaperture with the reflective layer. The reflective layer can enhance thelight collection efficiency of the image sensor.

Optionally, a series of color filter layers could be located upon thepatterned on the apertures. The color filter layers would be registeredwith respect to the photosensor regions. The series of color filterlayers could typically include either the primary colors of red, greenand blue, or the complementary colors of yellow, cyan and magenta. Theseries of color filter layers could comprise a series of dyed orpigmented patterned photoresist layers that are intrinsically imaged toform the series of color filter layers. Alternatively, the series ofcolor filter layers may comprise dyed or pigmented organic polymermaterials that are otherwise optically transparent, but extrinsicallyimaged while using an appropriate mask layer. Alternative color filtermaterials may also be used.

FIG. 6 shows an embodiment of a dual photodiode under each aperture.Preferably, under each aperture there are 2 photodiodes PD_(B) (orPD_(R)) and PD_(W-B) (or PD_(W-R)). Each photodiode captures chargecarriers excited by light of different wavelengths: λ_(B) (or λ_(R)) andλ_(w-B) (or λ_(w-R)). The topology of the two photodetectors(photodiodes) is such that the carriers from different regions of thespectrum do not cross talk. This can be accomplished by creatingphysical barriers such as trenches or by doping to form high resistiveareas.

To achieve the good light detection, it is desirable to create a goodcoupling of light to the photodiode. In one embodiment, this can beachieved by placing a microlens on top of the pixel, or creating amonolithic coupler. No color filter may be used in the embodiments ofthe image sensor with or without the microlens or optionally, asexplained above, color filter could also be used in the embodiments ofthe sensor with or without the microlens.

The microlens should to be placed at the appropriate height such as thelight is preferably focused on top of the light pipe. FIG. 7 shows aschematic of the microlens positioned at the optimum distance (z) byusing a polymeric layer of certain thickness as a spacer. Light is thenfocused on top of the light pipe which then directs it to thephotodiode. Microlens in this embodiment could be created using thestandard method used for CMOS sensors.

FIG. 8(A) to (C) show a monolithic coupling structure that can be formedby filling the lens material in a deeper etch. FIG. 8(A) shows that theapertures have a deeper etch, and the light pipe does not extend to thetop of the structure. FIG. 8(B) shows the area on top of the light pipeis filled with a polymer of the appropriate surface tension andviscosity to form lens in the normal process used to form microlenses.FIG. 8(C)(top) shows a plurality of the monolithic coupling structuresand FIG. 8(C) (bottom) shows a plurality of microlenses patterned on aplurality of light pipe apertures.

The microlenses of the embodiments of the image sensor may comprise anyof several optically transparent lens materials that are known in theart. Non-limiting examples include optically transparent inorganicmaterials, optically transparent organic materials and opticallytransparent composite materials. Most common could be opticallytransparent organic materials. The microlens layer could be formedincident to patterning and reflow of an organic polymer material thathas a glass transition temperature lower than the series of color filterlayers (if present) or the patterned planarizing layer (which isgenerally present in the embodiments of the image sensors).

The recognition of color and luminance by the embodiments of the imagesensors could be done by color reconstruction. Each compound pixel hascomplete luminance information obtained by combining its twocomplementary outputs. As a result, the same image sensor can be usedeither as a full resolution black and white or full color sensor.

The color reconstruction could be done to obtain full color informationby the appropriate combination of two adjacent pixels, which could beone embodiment of a compound pixel, either horizontally or vertically.The support over which color information is obtained is less than thedimension of two pixels as opposed to 4 for the Bayer pattern.

Each physical pixel of a device containing an image sensor of theembodiments disclosed herein would have two outputs representing thecomplementary colors, e.g., cyan, red (C, R) designated as output type 1or yellow, blue (Y, B) designated as output type 2 as shown in FIG. 9.These four outputs of two pixels of a compound pixel can be resolved toreconstruct a full color scene of an image viewed by a device containingthe image sensors of the embodiments described herein.

The foregoing detailed description has set forth various embodiments ofthe devices and/or processes via the use of diagrams, flowcharts, and/orexamples. Insofar as such diagrams, flowcharts, and/or examples containone or more functions and/or operations, it will be understood by thosewithin the art that each function and/or operation within such diagrams,flowcharts, or examples can be implemented, individually and/orcollectively, by a wide range of hardware, software, firmware, orvirtually any combination thereof. In one embodiment, several portionsof the subject matter described herein may be implemented viaApplication Specific Integrated Circuits (ASICs), Field ProgrammableGate Arrays (FPGAs), digital signal processors (DSPs), or otherintegrated formats. However, those skilled in the art will recognizethat some aspects of the embodiments disclosed herein, in whole or inpart, can be equivalently implemented in integrated circuits, as one ormore computer programs running on one or more computers (e.g., as one ormore programs running on one or more computer systems), as one or moreprograms running on one or more processors (e.g., as one or moreprograms running on one or more microprocessors), as firmware, or asvirtually any combination thereof, and that designing the circuitryand/or writing the code for the software and or firmware would be wellwithin the skill of one of skill in the art in light of this disclosure.In addition, those skilled in the art will appreciate that themechanisms of the subject matter described herein are capable of beingdistributed as a program product in a variety of forms, and that anillustrative embodiment of the subject matter described herein appliesregardless of the particular type of signal bearing medium used toactually carry out the distribution. Examples of a signal bearing mediuminclude, but are not limited to, the following: a recordable type mediumsuch as a floppy disk, a hard disk drive, a Compact Disc (CD), a DigitalVideo Disk (DVD), a digital tape, a computer memory, etc.; and atransmission type medium such as a digital and/or an analogcommunication medium (e.g., a fiber optic cable, a waveguide, a wiredcommunications link, a wireless communication link, etc.).

Those skilled in the art will recognize that it is common within the artto describe devices and/or processes in the fashion set forth herein,and thereafter use engineering practices to integrate such describeddevices and/or processes into data processing systems. That is, at leasta portion of the devices and/or processes described herein can beintegrated into a data processing system via a reasonable amount ofexperimentation. Those having skill in the art will recognize that atypical data processing system generally includes one or more of asystem unit housing, a video display device, a memory such as volatileand non-volatile memory, processors such as microprocessors and digitalsignal processors, computational entities such as operating systems,drivers, graphical user interfaces, and applications programs, one ormore interaction devices, such as a touch pad or screen, and/or controlsystems including feedback loops and control motors (e.g., feedback forsensing position and/or velocity; control motors for moving and/oradjusting components and/or quantities). A typical data processingsystem may be implemented utilizing any suitable commercially availablecomponents, such as those typically found in datacomputing/communication and/or network computing/communication systems.

The herein described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures aremerely exemplary, and that in fact many other architectures can beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality,and any two components capable of being so associated can also be viewedas being “operably couplable,” to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to optical coupling to permit transmission of optical light,for example via an optical pipe or fiber, physically interactingcomponents and/or wirelessly interactable and/or wirelessly interactingcomponents and/or logically interacting and/or logically interactablecomponents.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “a system having at leastone of A, B, or C” would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.”

All references, including but not limited to patents, patentapplications, and non-patent literature are hereby incorporated byreference herein in their entirety.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

We claim:
 1. An image sensor comprising an optical pipe, wherein theimage sensor is configured to provide a separation of an electromagneticradiation beam incident on the image sensor at a cutoff wavelengthwithout any external filter, wherein the optical pipe comprises a coreand a cladding, and wherein the optical pipe transfers electromagneticradiation incident on the image sensor to a photosensitive element on orwithin the substrate of the image sensor.
 2. The image sensor of claim1, wherein the core comprises a first photosensitive element.
 3. Theimage sensor of claim 2, further comprising a second photosensitiveelement coupled to the cladding.
 4. The image sensor of claim 1, whereinthe core has a core index of refraction (n₁), the cladding has acladding index of refraction (n₂), and further wherein n₁>n₂.
 5. Theimage sensor of claim 1, wherein the optical pipe is configured toseparate wavelengths of an electromagnetic radiation beam incident onthe image sensor at a cutoff wavelength through the core and thecladding.
 6. The image sensor of claim 3, wherein the secondphotosensitive element is located on or within a substrate.
 7. The imagesensor of claim 1, further comprising a lens structure or an opticalcoupler over the optical pipe, wherein the lens structure or the opticalcoupler is operably coupled to the optical pipe.
 8. The image sensor ofclaim 1, wherein the core comprises a first waveguide.
 9. The imagesensor of claim 1, wherein the cladding comprises a second waveguide.10. The image sensor of claim 1, further comprising a stack surroundingthe optical pipe, the stack comprising metallic layers embedded indielectric layers.
 11. The image sensor of claim 10, wherein a surfaceof the stack comprises a reflective surface.
 12. The image sensor ofclaim 1, wherein the image sensor is a complementary metal oxidesemiconductor (CMOS) image sensor.
 13. The image sensor of claim 10,wherein the core has a core index of refraction (n₁), the cladding has acladding index of refraction (n₂), and the stack has a stack refractiveindex (n₃), and further wherein n₁>n₂>n₃.
 14. The image sensor of claim1, wherein the photosensitive element comprises a photodiode.
 15. Animage sensor comprising an optical pipe, wherein the image sensor isconfigured to provide a separation of an electromagnetic radiation beamincident on the image sensor at a cutoff wavelength without any externalfilter, wherein the optical pipe comprises a waveguide, wherein theoptical pipe transfers electromagnetic radiation incident on the imagesensor to a photosensitive element on or within the substrate of theimage sensor.
 16. The image sensor of claim 15, wherein the optical pipetransfers electromagnetic radiation incident on the image sensor to aphotosensitive element on or within the substrate of the image sensor.17. The image sensor of claim 15, further comprising a lens structure oran optical coupler over the optical pipe, wherein the lens structure orthe optical coupler is operably coupled to the optical pipe.
 18. Animage sensor comprising an optical pipe, wherein the image sensor isconfigured to provide a separation of an electromagnetic radiation beamincident on the image sensor at a cutoff wavelength without any externalfilter.
 19. The image sensor of claim 18, wherein the optical pipetransfers electromagnetic radiation incident on the image sensor to aphotosensitive element on or within the substrate of the image sensor.20. The image sensor of claim 18, wherein the optical pipe comprises acore and a cladding.